So what's the difference between a model and an Angel? It comes down to contracts, and extreme dedication to the brand.

Being an Angel comes with certain obligations.

These ladies have special contracts with Victoria's Secret, meaning they have obligations to the brand that a runway model may not. This is why you'll see the Angels in Victoria's Secret campaigns, on talk shows, and in nearly every major runway show, including the Victoria's Secret Fashion Show.

The lingerie leader does not explicitly share the details of an Angel's obligations to Victoria's Secret, or how the contract differs from other Victoria's Secret models. However, when Ed Razek — chief marketing officer of the brand — addressed the departure of former Angel Doutzen Kroes on an Instagram post that is no longer available, he said, "Doutzen had a lucrative opportunity in Europe and it would have conflicted with her VS obligations. So, at her agency's request, we released her from contract. There was no conflict. No animosity."

While those "obligations" are not clearly spelled out, it can be assumed that the Angels must prioritize Victoria's Secret to an extent.

When Miranda Kerr ended her Angel gig of six years back in 2013, she explained that the time commitment is pretty intense. "It's three months at bare minimum," she told the Sydney Morning Herald. Fifty days may not seem like a lot, but those fifty days could interfere with other work opportunities.

Karlie Kloss also left the brand to puruse other opportunities, according to an Instagram post by Ed Razek. He said that she wanted to free up her time to attend NYU, indicating that her Angel commitments would interfere with school. Since leaving, she has continued modeling, has become an entrepreneur by starting her own Youtube channel, and has initiated a charity program called Kode with Klossy that teaches girls how to code.

A model's Angel status can be quite lucrative, but the pay has reportedly decreased.

Angels get the big bucks. Eleven of the 17 women on Forbes' list for The Highest Paid Models 2016 have been Victoria's Secret Angels. Keep in mind that this list does not break down how much of their earnings come directly from Victoria's Secret — it includes other contracts and endorsements, too.

Iconic models like Gisele Bündchen and Adriana Lima, who have more seniority with the brand, lead the pack. Bündchen finished last year with $30.5 million and Lima with $10.5 million, whereas newer Angels like Taylor Hill and Jasmine Tookes earned $4 million. It's likely a reflection of seniority when considering the paychecks of other Victoria's Secret Angels who also topped the list — Alessandra Ambrosio ranked in at $5 million and Karlie Kloss at $10 million.

These numbers are clearly high, but sources say that Angel contracts pay significantly less than they have in the past. In 2015, a source told Page Six that "Older contracts like Alessandra Ambrosio used to be in the millions, now they're like $100,00." There are a lot of factors, but the exposure and reputation of the women affiliated with Victoria's Secret is what seems to open the door for increased financial opportunities. After all, there have only been 36 Angels ever, according to Vogue Australia, so these ladies are definitely in high demand.

We also can't ignore the exceptions, such as Gigi Hadid and Kendall Jenner who are not Angels (though they have modeled for the brand), but have also made the Forbes Highest Paid Models 2016 list.

Becoming an Angel doesn't happen overnight.

We don't know the secret formula, but there does seem to be an unofficial right of passage to signing the coveted contract. In fact, many of the Victoria's Secret models who became Angels started shooting with the brand before they ever auditioned for the annual Victoria's Secret Fashion Show.

Supermodel Elsa Hosk reveals in her VS All Access video that her introduction to the lingerie company was through PINK, the youthful sister brand of Victoria's Secret. "I was on every single shoot with PINK for about three years," she said.

That dedication paid off, because in 2015, the 26-year-old model joined the ranks of longtime Victoria's Secret Angels Adriana Lima and Alessandra Ambrosio.

"Becoming an Angel means you are officially part of the family of Victoria's Secret and you are a spokesperson for the whole brand, and that is such a cool thing because it's one of the biggest, most amazing brands in the world," Hosk said in the video.

Angel Taylor Hill had a similar success story. After kicking off her career by modeling for PINK, and later, walking the runway in the 2014 Victoria's Secret Fashion Show, Hill was eventually promoted to an Angel in 2015, when she was only 19 years old.

Walking the Victoria's Secret Fashion Show is a start, but it doesn't guarantee Angel status.

Although popular models like Gigi and Bella Hadid have booked PINK campaigns and had the honor of rocking the Victoria's Secret Fashion Show runway alongside Hill and Hosk, they do not carry the same prestigious title — at least not yet.

In fact, when Gigi and Kendall Jenner both wore wings on the runway in 2016, people were upset because some of the official Angels — namely Martha Hunt — walked the runway without wings, as reported by Elite Daily. Just because a model walking for the Victoria's Secret runway gets to wear wings does not mean she is an Angel.

Gigi and Bella are runway regulars, but they are not Angels. Pascal Le Segretain/Getty Images